#include <stdio.h>
#include <stdlib.h>
int main()
{
    int i,j;
    int x = 0;
    int y = 5;
    int velocity_x = 1;
    int velocity_y = 1;
    int left = 0;
    int right = 20;
    int top = 0;
    int bottom = 10;
    while (1)
    {
        x = x+velocity_x;
        y = y+velocity_y;
        
        system("cls");   
        
        for(i=0;i<x;i++)
            printf("\n");
        for (j=0;j<y;j++)
            printf(" ");
        printf("o"); 
        printf("\n"); 
        
        if ((x==top)||(x==bottom))
            velocity_x = -velocity_x;
        if ((y==left)||(y==right))
            velocity_y = -velocity_y;        
    }    
}
